1. Field of the Invention
This invention relates, in general, to tumbler wheels for combination locks, and in particular, to a tumbler wheel having a plurality of random false gates, and a method and apparatus for making the same.
2. Description of the Related Art
A combination lock typically comprises a rotatable dial on the outside end of a spindle which is coupled through the lock's housing or a safe door to a set of annular tumbler wheels, each provided with a gate in its outer periphery and so interconnected to the other tumblers by dogs and lost-motion couplings that the gates of the tumblers can be aligned with one another by a predetermined series of manipulations of the dial corresponding to the lock's combination. When all of the gates are aligned relative to a fence lever, a fence on the lever drops into the slot formed by the aligned gates to permit a nose on the fence lever to engage a notch in a cam wheel, also coaxially mounted to the lock's spindle, which, upon further rotation of the dial, withdraws the lock's bolt from within a recess to open the lock or door. One such a combination lock is described in U.S. Pat. No. 176,876 to D. K. Miller.
Paralleling the implementation of these locks has been the development by unauthorized persons of means for gaining illicit entry to the contents protected by these locks. Typically, these means include gaining visual access, either directly or radiographically, to the tumbler wheels to ascertain the relative location of their gates, or by means of "touch" or "feel", in which the unauthorized manipulator obtains information about the wheels' gate locations from audible or tactile sensing of the minute vibrations caused by engagement between the cam wheel and nose part, or between the fence lever and the external peripheries of the tumbler wheels, when the dial is manipulated from without the lock.
Over the years, various efforts have been made to defeat the picklock's methods. It is known, for example, to provide the tumbler wheels of a combination lock with a plurality of false gates, each of which has a radiographic image identical or substantially similar to that of the wheels' true gate, such as is disclosed in U.S. Pat. Nos. 3,983,727 to Todd, 2,016,487 to Doenges, or 2,856,765 to Sreb. In another example of this art, U.S. Pat. No. 3,098,376 to Miller, radiographic compromise of the lock is resisted by means of the inclusion of a number of false tumbler wheels situated proximally of the lock's true tumbler wheels.
Similar efforts have been made to deny the picklock information about the wheels' gate location by use of sound or touch. An early example of this is to be found in U.S. Pat. No. 8,593 to Rickards, et al., in which a tumbler wheel of the lock is provided with a series of palpable notches to foil efforts at tactile manipulation by the picklock. In another example, U.S. Pat. No. 1,655,840 to Nichin, the tumbler wheels are provided with a plurality of notches which are caused to ratchet over a rib to set up a clicking noise when the lock's dial is rotated so as to camouflage the sound of the tumbler wheels' engagement with the fence lever. Maynard, in U.S. Pat. No. 3,106,083, discloses a combination lock in which operational parts are made of sound-deadening materials.
In addition to the use of false gates, it is also known to provide mechanisms within a combination lock whose purpose is to retain the fence lever in a position of disengagement from the tumbler wheels and/or cam wheel, except for a single point in one revolution of the lock's spindle, at which point the fence lever is biased into momentary contact with the peripheries of the tumbler wheels and/or the cam wheel. If, at this point in the lock's manipulation, the gates of the tumbler wheels are not in alignment with the fence of the fence lever, subsequent rotation of the dial retracts the fence lever from further contact with the cam or tumbler wheels such that continuous tactile or audible information concerning the gate's location becomes unavailable. Such an apparatus is described in U.S. Pat. No. 3,968,667 to Gartner, et al. These devices, when used in conjunction with tumbler wheels having false gates, render the combination lock highly tamper resistant.
Unfortunately, developments by unauthorized lock-pickers have not lagged far behind those whose purpose it is to defeat their efforts at illegal entry. Thus, a method is known by some few, but highly sophisticated, lock breakers to overcome even those combination locks equipped with both fence lever control devices and false-gated tumbler wheels. The equipment employed in this technique is sophisticated and two-fold: first, an apparatus exists which is capable of a very rapid external manipulation of the lock's dial in a predetermined manner which is programmable, and capable of dialing a complete combination for a three-wheel lock at a rate of 10 seconds per combination.
Coupled with this device in the illicit method is the use of a sophisticated sound wave analyzer which is acoustically coupled to the lock during its manipulation. Thus, by a rapid manipulation of the lock's spindle by the dialing apparatus, the fence lever control mechanism can be brought repeatedly into contact with the outer periphery of the tumbler wheels at successive angular positions of the wheels in a kind of "tapping" motion, which is then sensed by the wave analyzer. By having previously procured and analyzed a specimen of the particular lock to be picked, including those having false-gated tumbler wheels, the unauthorized manipulator will already have at hand a sound exemplar for use by the analyzer for comparison purposes to permit it to distinguish between the true and false gates on each tumbler wheel and to predict the accurate location of the true gate in each wheel. The dialing machine can then be programmed to quickly dial all possible permutations of the tumbler wheels which bring these predicted locations in alignment with the fence lever and the lock quickly opened.